Manufacture of soluble phosphates.



No. 689,286 Patented Dec. I7, 4913!.

6. DE CHALMOT.

MANUFACTURE OF SOLUBLE PHOSPHATES.

(Application filed Dec. 21, 1895. Rnnewed Nov. 28, 1901.}

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No. 689,286. I Patented Dec. l7, IQDI.

6. DE CHALMDT. MANUFACTURE OF SOLUBLE PHOSPHATES.

{Application filed Dec. 21, 1895. Renewed Nov. 23, 1901.) (No Model.) 3 Shaets-Shaet 2.

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No. 589,286. Patented DBO. l7, 190i.

G. DE CHALMUT.

MANUFACTURE OF SOLUBLE 'PHOSPHATES.

{Application filed Dec. 21, 1895. Renewed Nov. 28, 1991.

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GUILLAUME DE CHALMOT, OF LEAKSVI LLE, NORTH CAROLINA, ASSIGNOR TO WILLSON LABORATORY COMPANY, OF NEW YORK, N. Y., A CORPORA- TION OF WEST VIRGINIA.

MANUFACTURE OF SOLUBLE PHOSPHATES.

SPECIFICATION forming part of Letters Patent No. 689,286, dated December 17, 1901 Application illed December 21, 189.5. Renewed November 23, 1901. Serial No. 83,456. (No specimens.)

To all whom it may concern:

Be it known that I, GUILLAUME DE CHA MOT, a subject of the Queen of the Netherlands, (but having declared my intention of becoming a citizen of the United States,) re-' siding in Leaksville, in the county of Rockingham and State of North Carolina, have invented certain new and useful Improvements in the Manufacture of Solubie Phosphates, of which the following is a specification.

This invention relates to the treatme'nt of natural phosphates or phosphate-rock for the purpose of rendering the phosphoric acid therein soluble and available as plant-food.

My invention is based upon the discovery that if natural phosphates and sand are heated togetherin an electric furnace, much of the anhydrous phosphoric acid is driven OE, and if the mixture is not heated too long some phosphoric acid will remain in the residue in a much more soluble form.

My invention therefore involves the treatment of natural phosphates by mixing the same with silica and heating in an electric .'fu'rnace, removing the material from the furnace as fast as it becomes molten, and then bringing the heated material into contact with a further quantity of silica. The phosphoric acid which is driven off is conducted into contact with moist lime or phosphate-rock or is otherwise fixed or recovered. I have practiced this process with red phosphate-rock containing about twenty-three per cent. phosphoric acid, of which 1.39 per cent. is soluble in Wagners citrate solution. This phosphate I have coarsely pulverized and commingled with it about five per cent. of sand. This mixture I have fed to an electric-arc furnace consisting of a carbonhearth or crucible and a carbon pencil or slab arranged above it and adjustable vertically, the hearth and pencil being connected, respectively, to the opposite terminals of a suitable dynamo under conditions such as are commonly provided for the operation of furnaces for electric-arc smelting. The material is fed to the furnace at such rate that almost immediately after it becomes molten it overflows and the molten material runs out of the furnace, the object being that the phosphate shall not remain too long subject to the high heat of the electric furnace after it once becomes molten, as by so doing too much phosphoric acid would be driven oif to make the residue valuable as a fertilizer. The overflowing molten phosphate is caused to fall upon sand and is cooled, preferably, by dropping itin'to water, after which it is ground. I have found this residue to contain about 8.5 per cent. phosphoric acid, of which 4.29 percent. is soluble in Wagners citrate solution.

The difference between the original twentythree per cent. and the residual 8.5 per cent. of phosphoric acid is that which has been driven off during the fusing operation, and this I recover by causing it to pass over trays containing moistlime or, preferably, coarselybroken and moistened phosphate-rock,whereby the anhydrous phosphoric acid is taken up, forming dibasic or monobasic calcium phosphates which are highly available as plantfood.

My process yield-s highly-concentrated and available phosphatic fertilizers from lowgradeiphosphate-rocks without the use of sulfuric acid, orthe anhydrous phosphoricacid vapors may also be conducted over or through water, and the metaphosphoric acid thus formed may be sold as such.

The accompanying drawings show a form of furnace which is adapted for the practice of my process.

' Figure 1 is a vertical transverse section on the line 1 l in Fig. 2. Fig. 2 is a front elevation, partly in vertical section, on the line 2 2 in Fig. 1. Fig. 3 is a vertical transverse section on the line 3 3 in Fig. 1. Fig. 4 is a sectional elevation, on a smaller scale than Fig. 1, showing the inclosing of the working partsin a casing B. Fig. 5 is a longitudinal mid-section of the cylinder L.

Referring to the drawings, let A designate the hollow hearth or crucible of the furnace, and B the carbon pencil thereof. The hearth A has a bottom layer of carbon 0, and beneath this a conducting-plate 01., preferably of iron, through which the current may enter or leave the furnace. The walls of the furnaceie arth may be made of fire-brick or other refractory material and may be lined or not with carbon. The carbon pencil B is r a massive block or slab of carbon and is adjustable up and down through a suitable hole in the roof or crown of the furnace. It is best constructed by being built up of slabs or bars of carbon held in a holder or clamp 0, carried by a vertically-adjustable rod I),

hung from suitable adjusting mechanism.-

nace-chatnber extends an outlet-flue F,which leads to a chamber G, in which are placed alternating-trays g 9, containing lime, phosphate-rock, or other material for absorbing the phosphoric acid which passes out from the furnace through the flue F, or these trays may contain water, over which or through which the fumes from the furnace may be caused to pass. From the chamber G the fumes enter a chimney H, which is of such height and construction as to afford a draft sufficient to carry off from the furnace-chamber all phosphatic fumes, while at the same.

time the draft should not be sufficient to draw up air into the furnace through the opening e. Instead of the chimney II any suitable draft or suction apparatus may be provided, as is well understoodin furnace practice.

It is desirable to admit some air to the flue F in order to oxidize any phosphorous vapors or phosphorous acid which may have been formed in the furnace by partial reduction of the phosphoric acid. For this purpose I provide an air-inlet flue I, controlled by a door or damper I, whichmay be more or less opened and entering the flue F through an opening or twyer i. I have shown a chain 25 as a means of adjusting the opening of damper I.- The flue I preferably traverses the "fine F for a sufficient distance to somewhat heat the entering air. The material is fed into the furnace by being put into hoppers J J, from the bottoms of which fiues K K lead downward and discharge obliquely into the furnace-chamber on opposite sides of the carbon pencil. These lines are controlled by 'slidesjj.

Beneath the overflow-wall E is arranged a hollow cylinder L,"preferably of iron plate, and above this-is a hopper M, containing sand. This hopper has some suitable means for feeding'out the sand, so that it may fall on the cylinder. I have shown a hopper with two feed-rollers m m and slides n 'n for controlling the flow. The sand fromv the roller m falls on the cylinder before the phosphate can fall upon it, a plate It being arranged to prevent the sand from dropping off the cylinder. The sand from the'roller m falls on the cylinder after the latter has passed beneath the opening (2. The result-of this arrangement is that as the cylinder L slowly revolves in the direction of the arrow its surface is sprin kled with a suitable layer of sand from roller m. The molten phosphate which flows out from the furnace falls upon this layer of sand, which protects it from direct contact with the iron cylinder, so that it cannot burn to the cylinder. The cylinder then receives a sprinkling of sand from roller m to cover the phosphate. The phosphate finallydrops 0E into a tank P beneath, which tank preferably contains water and is hung upon trunnions in order that when full it may be overturned to dump the phosphate upon a grating Q, beneath it. Beneath the grating is a gutter 1) to carry off the water.

The operation is as follows: The ground phosphate-rock, mixed with a suitableproportion of sand or other silica, is filled into the hoppers J J. In starting the operation the carbon pencil B is lowered to the hearth-' lining 0, some of the ground material is dumped into the furnace-chamber on each side of the carbon pencil, the electric current is started, and the pencil is slightly lifted to form an arc, the heat of which fusesthe phosphate, and the pencil is then gradually lifted,

' while more material is continually fed in until a pool of molten phosphate is accumulated in the furnace as high as the wall E. The op -eration is now started and may be carried on continuously. It is only necessary to gradually supply, the material from the hoppers and keep the carbon pencil adjusted so as to maintain the are properly, the sup ply of material being graduated so that it will displace the phosphate about as fast as the latter becomes molten, thereby causing the molten phosphate to continuously flow out over the wall E and fall upon the cylinder L, which, as stated, is caused to slowly revolve in the direction of the arrow and which is kept supplied with a surface coating of sand from the hopper M. A further layerof sand is sprinkled over the phosphate after the latter has fallen or while it is falling onto the cylinder, thereby more effectually combining the sand with the molten phosphate. The phosphate hardens upon the cylinder, and as the latter turns it is dumped while still very hot into the water in the tank P, whereby it is instantly cooled and cracked in all directions, so that it becomes friable,

oifby the gutter p. Thephosphate is then hydrous phosphoric acid which passes off from the furnace. The arrangement of the trays in zigzag manner, as shown, causes the fumes to be circulated into intimate contact with the calcareous material. The remaining gases pass into the chimney H, whereby they are carried away, or the gases may then be drawn through water or otherwise treated to remove from them any uncombined residue of phosphoric acid.

I make no claim in this application to the apparatus here shown, as that is claimed in another application which I have prepared, filed December 24:, 1895, Serial No. 573,214,

patented August. 17, 1897, No. 588,267; nor

do I make any claim in this application to the process of increasing the proportion of soluble phosphoric acid in phosphate-rock by simple fusion in an electric furnace, as that process is claimed by me in another application, filed December 20, 1895, Serial No. 572,735.,patented August17,1897, No. 588,266; nor do I claim in the present application the overflowing of molten phosphate from the furnace or receiving the overflowing phosphate upon a layer of sand. My present invention is directed to the fusing together of phosphate-rock or other natural phosphates with sand or other form of silica, whereby a part of the phosphoric acid is driven ofi. So far as I am aware I am the first'to melt phosphate-rocks with sand, so as to drive 0E anhydrous phosphoric acid and render the remaining phosphoric acid more available. I believe also that I am the first to discover that by heatin g calcium phosphate and silica in an electric furnace much anhydrous phosphoric acid is driven off. I have found that I if the phosphate is exposed to the are after itis molten the amount of phosphoric acid,and especially of available or soluble phosphoric acid, rapidly decreases.

V is desirable to discharge the phosphate from the furnace as quickly as possible after it becomes molten. In view of these facts I am disposed to advance the hypothesis, as explaining the rationale of my process, that tribasic calcium phosphate and silica form first silico phosphate. of lime and that afterward the excess of silica gradually replaces the phosphoric acid. Electrolysis of the phosphate I believe to be undesirable, as tending to reduction of the phosphate. On this account I consider it preferable to use the alternating current, which avoids electrolysis, although I do not confine myself to such current. p

The fusing of the phosphate and silica ac- For this reason it.

cording to my invention in an electric furnace has great practical advantage over any possible treatment thereof in a shaft-furnace, since in the latter case not only must a flux be added, but the carbon and carbon monoxid necessarily employed in a shaft-furnace act to reduce the phosphoric acid. In the electric furnace, on the contrary, the only reduction can come from the surfaces of the carbon pencil, which have been converted into graphite by the high temperature of the electric arc, and the reduction thus occasionedis very slight. Most of the reduction, in fact, occurs at the bottom of the hearth, near the carbon lining 0; but the phosphate which is thus reduced remains in the furnace and forms a somewhat permanent base for the molten phosphate above, which is caused to flow out as fast as it fuses.

If desired, the electric furnace may be entirely inclosed, so as to prevent air being drawn into it, in which case any suitable shell maybe built around it, as shown in Fig.

'41, where R is the shell or casing, which should be provided with suitable windows and doors; or, if desired, the carbon pencil alone maybe inclosed, as indicated in dotted lines in Fig. 1, by building annpright chamber around the pencil high enough to admit of the highest adjustment of the pencil and having a hole in its top through which the carbonholding rod carrying the pencil may freely pass.

The cylinder L being made hollow will cool itself by radiation, or it may be cooled by water in any known way, as by playing a hose on it or by circulating water in it, as shown, for example, in Fig. 5, where q is the waterinlet pipe and r is the outlet or waste pipe.

The chamber G may be replaced by any other suitable absorption apparatus.

My invention is not limited to the use of an alternating electric current, as a continuous current may be used.

I claim as my invention the following-defined novel features, substantially as hereinbefore specified, namely:

1. The process of treating natural phosphate for increasing the proportionof soluble phosphoric acid, consisting in mixing the same with silica, fusing the mixture in an electric furnace, removing it from the fu rnacc as fast as it becomes molten, and then bringing the heated material into contact with a further quantity of silica.

2. The process of treating natural phosphate which consists in mixing it with silica, fusing it in an electric furnace, whereby anhydrous phosphoric acid is driven off, and passing the fumes from the furnace into contact with moist calcareous material, whereby a soluble calcic phosphate is formed.

3. The process of treating natural phosphate which consists in mixing it with silica, fusing it in'an electric furnace, whereby anhydrous phosphoric acid is driven ofi, draw- .iro

ing the fumes from the furnace, mixing air my name in the presence of two subscribing therewith to oxidize any reduced phosphoric witnesses.

acid and then assin the fumes into contact with a. mat rial capable of absorbing or DE OHALMO 1 5- combining with the anhydrous phosphoric Witnesses:

acid. J. M. HOPPER, In witness whereof I have hereunto signed S. P. J ARRETT. 

